Cystic fibrosis is a fatal disease caused by a defective gene which codes for cystic fibrosis transmembrane conductance regulator (CFTR), a glycoprotein important in chloride transport. Approximately 75% of patients with CF carry a deletion of phenylalanine from position 508 (F508) of the coding sequence for CFTR. This mutant CFTR is incompletely processed within the endoplasmic reticulum with limited transport of nonfunctional CFTR to the surface of airway epithelial cells, thereby causing defective chloride secretion via the protein.